This invention relates to metal tubing, and in particular to high precision metal tubing requiring a high degree of environmental protection and methods of making such tubing. Exemplary of such tubing is O'Brien MJ tubing.
The need for protecting metal tubing, and in particular high precision tubing used for instrumentation and control functions, from corrosion and failure in offshore/marine environments is recognized as acute. The problem is discussed, for example, in a technical paper by Chevron Energy Technology Company entitled “Materials Selection For Offshore Instrument Tubing,” incorporated herein by reference. Some of the surface contaminants causing corrosion in these applications include sea water, grinding dust, weld slag and microbial agents.
Numerous attempts to increase the corrosion resistance of these tubes have been made. One approach has been to tighten the 316 L metallurgy specification to require more molybdenum content than required per ASTM A269/A213. Others have encased the tubes in impervious plastic jackets. One such attempt is described in Shell Exploration & Production, “Gumusut/Kakap Project—Polyurethane Jacket for Offshore Stainless Steel Tubing,” 27 Feb. 2007, incorporated herein by reference. Despite the best efforts of many major companies, tubing failures remain a serious problem.